The disclosed method can find application in a networked simulation system having a plurality of simulation computers connected to one another via a network. Such simulation systems typically use the Distributed Interactive Simulation (DIS) standard IEEE1278 for distributing the data between the individual simulation computers. Such simulation devices are used for training the crew of land vehicles, such as construction machines or military vehicles, for example.
The networked simulation system has a plurality of display devices on which a shared virtual reality can be represented. Usually, one display device is allocated to each simulation computer. However, it is also possible for a plurality of display devices to be allocated to one simulation computer, in order to represent different views of the virtual reality, for example a view from a vehicle toward the front and a view toward the rear. Furthermore, it may be necessary to represent different views of the shared virtual reality if the simulation device is used by a plurality of simulation participants, as is the case in the parallel training of a plurality of crew members. Furthermore, it is possible to provide a plurality of display devices in which the same view is represented, e.g., in order to give a trainer the opportunity to track the virtual reality from the point of view of a simulation participant.
The virtual reality that can be perceived by the simulation participants on the display devices has a terrain formed by a multiplicity of polygons. In order that each simulation computer can carry out the calculations required for displaying the polygons on the display device, spatial coordinates of the polygons are kept in each simulation computer. For this purpose, the spatial coordinates can be transmitted via the network from another simulation computer or a server and can be stored on the respective simulation computer. In order to make the representation of the terrain appear more realistic, textures representing the surface of the terrain can additionally be mapped onto the polygons.
Changes of the terrain can be generated in the context of the simulations. By way of example, simulated land vehicles can leave tracks in the terrain. A construction machine or a military engineering vehicle can change the terrain by means of excavation work. In the field of military applications, the terrain can furthermore be changed by explosions or impacts of projectiles. The terrain change can firstly relate to the topology of the terrain, that is to say the arrangement of the polygons in the virtual reality. In addition, the texture mapped onto the polygons can also be changed in order to represent changes in the constitution of the terrain.
In the context of a networked simulation it is necessary, then, for the terrain changes calculated by a first simulation computer to be communicated to the other simulation computers, in order that the latter can represent the changes of the terrain on the display devices assigned to them. In the case of known simulation devices, for this purpose, on the first simulation computer, polygons of the changed region are subdivided into sub-polygons and the spatial coordinates thereof are calculated. The spatial coordinates are then transmitted via the network to the other simulation computers. On the basis of the spatial coordinates, the other simulation computers calculate a view of the virtual reality and display the latter on the corresponding display device. In order to be able to achieve a display of the change processes in real time, at least 60 frames per second have to be represented in each of the display devices. The method described above has the disadvantage here that the volume of spatial coordinate and polygon data to be transmitted is so large that there is no guarantee that the data can be transmitted via the network in the transmission time required for a real-time representation.